Some electrohydraulic solenoids, for example those used in automotive systems, utilize tight running fits between the ferromagnetic core and the armature. In order to optimize response time, the core cavity in which the armature moves is sometimes vented to the surrounding environment. The surrounding environment may be an oil environment, and the venting fluid may be oil. Open communication between the core cavity and the environment may introduce environmental contaminants contained in the oil, such as ferrous particles, to the internal passageways of the electrohydraulic solenoid. The contaminants may build up forming a magnetic sludge that can inhibit armature movement.
Some conventional electrohydraulic solenoids rely on upstream filtering of the venting fluid, and may include filter screens in hydraulic sections of the solenoid. Conventional filtering has been shown to be insufficient as solenoid sensitivity to contaminants increases.
Accordingly, a need exists for a solenoid with a vent path having improved filtering capabilities.